Abstract: By collecting historical documents of drought and flood disasters in the Chuhe River Basin from 1644 to 1911, we established the yearly drought and flood level sequence during the Qing Dynasty. By using methods such as frequency analysis, moving average, and wavelet analysis, we examined the changes in drought and flood patterns in the basin spanning 268 years. The findings reveal that: 1) The climate evolution in the Chuhe River Basin during the Qing Dynasty is predominantly characterized by normal and partially waterlogged conditions. Following the early Qing Dynasty, cases of waterlogging and partial waterlogging surpassed those of drought and partial drought in the Basin. (2) Over the 11-year timescale, drought and flood disasters in the Chuhe River Basin during the Qing Dynasty can be divided into four distinct phases: 1644-1720, 1720-1760, 1760-1820, and 1820-1911. (3) The study identifies four primary cycles, approximately 9, 14, 28, and 55 years in duration. The strongest cycle features periodic oscillation around 55 years, followed by the 28, 14, and 9-year cycles. These research findings address existing knowledge gaps surrounding the Chuhe River Basin, enhance understanding of historical climate change, and offer guidance for the scientific utilization of water resources and disaster prevention efforts.

Key words: drought and flood disasters, Qing Dynasty, Chuhe River Basin, sequence reconstruction, time sequence analysis